Stent Delivery Device

ABSTRACT

A delivery device and method for use, the delivery device including a stent device, a restraining sheath, and a pull member. The restraining sheath is mounted coaxially over the stent device for maintaining the stent device in a delivery configuration, and may include a line of weakness extending axially. The pull member is to be pulled so as to split the restraining sheath at the line of weakness and withdraw the restraining sheath from over the stent device. The pull member and the line of weakness may be located on opposing sides of the restraining sheath. The pull member may have an inner part extending inside of the restraining sheath, an outer part extending outside of the restraining sheath, and a wrap around portion therebetween for wrapping around an axial end of the restraining sheath to radially capture the restraining sheath between the inner and outer parts.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/142,823, which was filed as a U.S. national stage application under35 USC §371 of International Application No. PCT/EP2009/064273, filedOct. 29, 2009, claiming priority to United Kingdom Patent ApplicationNo. 0823658.0, filed Dec. 30, 2008, and to U.S. Provisional ApplicationNo. 61/141,411, filed Dec. 30, 2008, each of which is incorporated byreference in its entirety into this application.

FIELD OF THE INVENTION

The present invention is concerned with a delivery device for releasinga stent device from a restraining sheath in order to deliver the stentdevice to a treatment site within a patient. The stent device isradially contained within the restraining sheath in a radially reduced,delivery configuration. The restraining sheath has to be released inorder that the stent device can be radially expanded into a deployedconfiguration for holding open a bodily lumen.

BACKGROUND OF THE INVENTION

Stent devices are used in the treatment of diseased human or animalbodily lumens to provide structural support to the lumens. Of particularrelevance to the present invention are stent devices for supporting andholding open vasculature lumens of the human body.

In order for the stent devices to reach the treatment site, a deliverydevice is used that passes through vascular passageways, oftentraversing relatively long and tortuous paths. Surgical procedures fordelivering stent devices to various locations in the body are known toone skilled in the art. Thin and flexible delivery devices areadvantageous for reaching challenging treatment sites.

With the objective of a reduced profile delivery device, a stent deviceis generally provided in a radially reduced delivery state. The stentdevice may be crimped onto an inner support member and a restrainingsheath is disposed over the stent device to maintain the stent device inthe radially reduced configuration. The delivery device will then be fedthrough relevant passages of the vasculature with the stent devicemaintained in the delivery configuration by the restraining sheath. Onceat the treatment site, the restraining sheath is operated upon so thatthe stent device can radially expand to a deployed configuration forsupporting and holding open a portion of a vein or artery or otherbodily lumen.

Stent devices have a structural framework for supporting a diseasedvasculature. Different arrangements for the structural framework arefound throughout the relevant art. Often, the stent device will beformed from a seamless tubular work-piece into an elongate device havinga number of axially spaced rings of stent material with each ring formedof zigzagging struts and with each ring connected to another by severalcircumferentially distributed connector struts. The inner major surface,the outer major surface or both may be covered to make the stent deviceliquid impermeable, which is then often named a stent graft. Theframework may, however, be uncovered, which is then often named a barestent.

Stent devices may be balloon expandable or they may be self-expandable.Balloon expandable stents may be radially expanded into the deployedconfiguration by action of a circumferential balloon disposed betweenthe inner member and the stent device. The balloon is inflated, usuallyby injection of saline solution, thereby expanding the stent device intothe deployed configuration. The present applicant has particularexperience with self-expandable stent devices. These can be made ofshape memory materials, such as the shape memory Nickel Titanium alloyknown as Nitinol. Nitinol can be constructed into a desired deployedconfiguration and then crimped into the reduced profile deliveryconfiguration. As long as the Nitinol stent device is kept below a solidphase transition temperature, the deformation of the reduced profiledelivery configuration will be kept. Once raised above the phasetransition temperature, such as at a body temperature, the Nitinol stentdevice will return to its original, radially expanded deliveryconfiguration when it is allowed to do so, that is when it is releasedby the restraining sheath.

The prior art is replete with examples of ways to release the stentdevice from the overlaying restraining sheath. Two examples areprevalent.

One example is to slide the restraining sheath over the stent device inorder to expose the stent device. The frictional forces between thestent device and the restraining sheath can be great, particularly asthe stent device becomes more highly crimped, which causes increasedradial forces straining on the sheath as it slides over the stentdevice. Similarly, a longer stent device will have greater frictionalcontact with the restraining sheath. This latter contributor to thefrictional forces between the restraining sheath and the stent device isimportant in applications where stent devices have lengths greater than200 mm and up to 300 mm or more. A pull member, extending proximally toa handle of the delivery device, is generally used to retract the outersheath by pulling on it to move the outer sheath relative to the stentdevice to expose the stent device. One example of this form of releaseof the stent device can be found from WO 2004/096091. The highfrictional forces involved in dragging the restraining sheath over thestent device can be damaging to the stent device and can make the pullforce required to move the restraining sheath undesirably high.

Another example of a general way to release a stent device is to tearthe restraining sheath axially along the stent device, thereby releasingthe stent device to radially expand. One or more perforation lines canbe provided in combination with a pull member running adjacent theperforation line or lines. As the pull member is pulled, the restrainingsheath is torn at the perforation line to radially release the stentdevice. We found U.S. Pat. No. 5,246,452, US 2008/0243224 and WO99/53865 to be interesting example disclosures of such technology. Alsoknown is the tearing of the restraining sheath by using a pull member tocut therethrough, such as with a wire pull member that is able to slicethrough the restraining sheath. An interesting example of this kind oftechnology is disclosed in EP 0732087. One difficulty with such releasemechanisms is that all or a part of the restraining sheath remainsbetween the stent device and a wall of the bodily lumen. This may not bedesirable in terms of properly engaging the stent device with the wallof the bodily lumen and may be disadvantageous in so far as it onlyallows certain materials to be used for the restraining sheath, whichare long-term biocompatible.

Accordingly, it is an objective of the present invention to provide amechanism for releasing a stent device from a restraining sheath thatremoves the restraining sheath from between the stent device and a wallof the vascular lumen and also allows a relatively low pulling force incarrying out the stent device release.

SUMMARY OF THE INVENTION

The present invention provides a stent delivery device, comprising:

a stent device, which is radially expandable from a radially reduced,delivery configuration to a radially expanded, deployment configuration;

a restraining sheath mounted coaxially over the stent device formaintaining the stent device in the delivery configuration;

the restraining sheath having a line of weakness extending axiallytherealong;

a pull member to be pulled so as to split the restraining sheath at theline of weakness and withdraw the restraining sheath from over the stentdevice;

characterised in that:

the pull member and the line of weakness are located on opposing sidesof the restraining sheath.

In the context of a restraining sheath mounted over a stent device, themeaning of opposing sides is easy to understand. Taking a cross-sectionof the restraining sheath, one half of that cross-section can beenvisaged, which is ninety degrees either side of the pull member. Theline of weakness will be located in the opposing half. Preferably, thecross-section could be split into quarters with one of the quarterscircumferentially centred on the pull member and in this case, the lineof weakness is located in an opposing quarter. Yet more preferably, theline of weakness and the pull member are located substantiallydiametrically opposite one another.

The opposing configuration allows just one pull member to be providedand still the sheath can be satisfactorily split and the restrainingsheath withdrawn in its entirety so it does not remain between a wall ofa bodily lumen and an outer major surface of the stent device. A reducedprofile configuration at the stent device can thus be provided.

The line of weakness can be provided in a number of forms. It could be aline of perforations, a reduced material thickness line, a join betweenopposing sides of the restraining sheath, etc. The line of weakness canbe axially straight, zigzag, sinusoidal, etc. If perforations are used,the perforations may be of any appropriate density and length and maynot necessarily extend all the way through the thickness of therestraining sheath, but may instead be sufficiently deep to provide thenecessary weakness. Important is that the line of weakness splits openwhen the pull tab is pulled during normal use of the delivery device.

The pull member has an inner part extending inside of the restrainingsheath, an outer part extending outside of the restraining sheath and awrap around portion therebetween for wrapping around an axial end of therestraining sheath for radially capturing the restraining sheath betweenthe inner and outer parts.

Capture of the restraining sheath in this manner offers a secure way tosplit and collect the split restraining sheath as it is withdrawn fromaround the stent device.

In one embodiment, the pull member is attached to the delivery deviceand fixed relative to the restraining sheath at one end and an opposingend provides a pull end to be pulled in order to effect splitting andwithdrawing of the restraining sheath. The pull member wraps around anaxial end of the restraining sheath between the opposing ends with theinner part extending inside thereof and the outer part extending outsidethereof.

Preferably, the stent device is supported on an inner member, whichextends proximally from the stent device. The fixed end of the pullmember may be attached to the inner member so that the pull memberextends therefrom inside of the restraining sheath, wraps around anaxial, preferably distal, end of the restraining sheath and returnsproximally on the outside of the restraining sheath to provide the pullend. Preferably, the restraining sheath is attached to the inner memberat a position proximal of where the fixed end of the pull member isattached.

In one preferred embodiment, at least a portion of the pull member is apolymer thread. Such a thread will offer an appropriate amount offlexibility and also allows a reduced profile construction. Preferably,the polymer thread is a polyamide thread. The thread is to have a tearstrength sufficient to remain intact while the restraining sheath splitsat the line of weakness.

Preferably, the pull member comprises a stiffer portion attached to thepolymer thread portion at a position proximal of the stent device. Forexample, the proximal portion could be made of metal. This ensures thatthe pull member has sufficient strength to perform its activationfunction and also sufficient flexibility where it is needed.

In another embodiment, the pull member forms a hook at one end and anopposing end provides a pull end to be pulled in order to effectsplitting and withdrawing of the restraining sheath. The hook is forradially capturing an inside and an outside of the restraining sheathbetween inner and outer parts thereof. A wrap around portion of the hookis for engaging the axial end of the restraining sheath.

Preferably, the hook is to be moved axially before it captures an axialend of the restraining sheath. In one preferred embodiment, the deliverydevice comprises a storage member adjacent an axial end of therestraining sheath, which includes a recess so that the hook is storedin a reduced profile configuration for delivery. The hook is axiallymovable out of the recess by pulling on the pull member, whereupon ittakes on a radially increased configuration for capturing therestraining sheath. The storage of the hook provides a guard against thehook damaging tissue during feeding of the stent device to the treatmentsite. Preferably, the pull member comprises a shape memory material,such as Nitinol, configured to expand the hook from the reduced profileconfiguration. Other ways of biasing the hook to the expanded positioncould, however, be used as would be clear to one skilled in the art,such as structural residency of the pull member material.

Preferably, the delivery device comprises a distal tip member.Preferably, the distal tip member provides the storage member and thusincludes the recess. Preferably, the distal tip member is attached to aninner member upon which the stent device is mounted and supported.

In the hook embodiment, at least a portion of the pull member axiallyextending between (radially) the restraining sheath and the introducersheath is flattened, thereby allowing a small profile delivery device.The pull member is stiff enough to ensure the hook maintains its hookform during withdrawal and splitting of the restraining sheath. In onepreferred embodiment, the pull member is made of metal.

It is preferred that the restraining sheath be formed of an axiallydrawn polymer material. Preferably, the sheath is cold drawn. Even morepreferably, the material is poly(ethylene terephthalate) (PET). It hasbeen found that such materials are particularly suitable for splittingand being withdrawn according to the mechanisms of the preferredembodiments of the present invention.

Also preferred is that there be a strip of protective material locatedradially between the line of weakness of the restraining sheath and thestent device. This allows the line of weakness to be formed by, forexample, laser and the stent device to be protected from damageoccurring as a result of the formation process.

The stent device is preferably formed from a seamless tube into aframework for supporting a bodily lumen. The framework may or may not becovered, for example, with ePTFE. The stent device is preferably of theself-expanding variety and made of a shape memory material, such asNitinol. The framework may be made up of a number of axially spacedcircumferential rings centred on the longitudinal axis of the stentdevice. Each of the rings may be joined to one another by severalconnecting struts. The rings may be formed of zigzagging strutsextending around the longitudinal axis of the stent device.

In the following, presently preferred embodiments of the invention aredisclosed with reference to the drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a delivery device of a first embodiment of the presentinvention, wherein an open loop of thread is used to capture arestraining sheath to affect splitting and withdrawal of the restrainingsheath from around the stent device.

FIG. 2 shows the delivery device of FIG. 1 with the restraining sheathpartially withdrawn and part of the stent device expanded.

FIG. 3 shows a delivery of a second embodiment of the present invention,wherein a pull member with a hook at a distal end is used to capture arestraining sheath to affect splitting and withdrawal of the restrainingsheath from around the stent device.

FIG. 4 shows the delivery device of FIG. 3 with the restraining sheathpartially withdrawn from around the stent device and a part of the stentdevice having been expanded.

FIG. 5 discloses a longitudinal axial section through a device forloading a stent into a delivery sheath.

FIG. 6 disclose the device of FIG. 5, but with the stent partiallyloaded in the sheath.

FIG. 7 discloses a flow diagram of method steps for installing a stentor stent graft within a sheath.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, a delivery device 1 is shown. The delivery devicehas a stent device 2 crimped onto an inner, tubular member 3. Arestraining sheath 4 is mounted coaxially over the stent device 2 andserves to maintain the stent device 2 in the reduced profile, crimped,delivery configuration. A push member 10 is provided proximal of thestent device 2 to hold the axial position of the stent device 2 on theinner member 3 as the restraining sheath 4 is withdrawn over the stentdevice 2. The restraining sheath 4, the stent device 2 and a distal endregion of the inner member 3 extend distally from a tubular introducermember 13.

The stent device 2 is of the self expanding variety and as such is madeof a shape memory material. In the preferred embodiment, the shapememory material is Nitinol. The stent device 2 will strain against therestraining sheath 4 as it is biased to revert to its expandedconfiguration when it is above its phase transition temperature. Thestent device 2 is made from a single tube of Nitinol and formed into adesired framework by laser cutting. The stent device 2 is formed into anumber of axially spaced rings of zigzagging struts centred on alongitudinal axis of the stent device 2. Each ring is joined to anotherby several connector struts. The stent device 2 may be of any lengthincluding lengths of up to 300 m, perhaps between 200 mm and 300 mm.

The restraining sheath 4 is, in the preferred embodiment, formed of colddrawn PET. This material has a desirable capability to crumple as thesheath 4 is withdrawn, thereby easing the withdrawal.

A mechanism is provided to affect release of the stent device 2. Thismechanism includes a pull member 5 and a line of weakness 6.

The pull member 5 includes an inner part 7 extending axially along aninside of the restraining sheath 4 and radially between the restrainingsheath 4 and the stent device 2. The pull member 5 further includes anouter part 8 extending axially along an outside of the restrainingsheath 4. The inner part 7 and the outer part 8 are connected by a wraparound portion 9 of the pull member 5 so that the restraining sheath iscaptured between the inner part 7 and the outer part 8. The wrap aroundportion 9 wraps around a distal end of the restraining sheath 4.

The inner part 7 is attached to the inner member 3 at a point proximalof the stent device 2 and the proximal push member 10. Glue can be usedto affect the attachment. The outer part 8 extends proximally beyond thestent device 2 and the push member 10 to provide a pull end of the pullmember 5, at a proximal end of the delivery device, which is usuallyprovided with a handle. The pull end of the pull member 5 is to bepulled upon in order to exert a proximal force on the restraining sheath4.

The pull member 5 includes a polymer thread portion 11 and a proximalstiffer portion 12. The polymer thread portion is, in the preferredembodiment a nylon thread, which is sufficiently flexible to extendinside the restraining sheath 4, wrap around a distal end of therestraining sheath 4 and return outside the restraining sheath 4. Thestiffer member 12 is made of metal in order to provide a sufficientlystrong material to transfer the necessary force for retracting therestraining sheath 4. The polymer thread portion 11 and the stifferportion 12 are connected by a connection member 14. The connectionmember 14 is, in the preferred embodiment, a shrink tube shrunk onto thestiffer portion 12 with the polymer thread 11 clamped therebetween. Theconnection between the polymer thread portion 11 and the stiffer portion12 occurs proximally of the restraining sheath 4, the stent device 2 andpush member 10. The stiffer portion 12 of the pull member 5 continues toextend proximally, perhaps back to a handle if one forms part of thedelivery device, to provide the pull end thereof. The pull end is to bepulled upon for actuating release of the stent device 2 from therestraining sheath 4.

The restraining sheath 4 is attached to the inner member 3 at a positionproximal of where the inner part 7 of the polymer thread 11 is attachedto the inner member 3. The outer part 8 of the polymer thread 11 is fedradially over the restraining sheath 4 and extends proximally beyondwhere the restraining sheath 4 is attached to the inner member 3. Inthis way, the pull member 5 forms an open loop extending around therestraining sheath 4 and extending proximally beyond the restrainingsheath 4 without having to pass through the restraining sheath 4.

A distal tip member 15 of the delivery device 1 is attached to a distalend of the inner member 3. The distal tip member 15 is bulbous ascompared to the inner member 3 and is tapered at its distal end. Thisconfiguration eases passage of the delivery device 1 through thevasculature of the body being treated.

The line of weakness 6 is, in the preferred embodiment, a straight lineof axially extending perforations formed in the restraining sheath 4 andprovided along the full length of the stent device 2 and to the distalend of the restraining sheath 4. The line of weakness 6 is disposeddiametrically opposite the inner and outer parts 7, 8 of the pull member5.

Furthermore, a protective strip 16 is positioned radially between theline of weakness 6 in the restraining sheath 4 and the stent device 2and extending the full length of the line of weakness 6. This allows theline of weakness to be formed after the restraining sheath 4 is disposedover the stent device 2, while protecting the stent device 2 from damageas a result of the formation of the line of weakness 6.

Accordingly, the restraining sheath 4 will have diametrically opposingbumps when viewed in cross-section as a result of the protective strip16 and the inner part 7 of the polymer thread portion 11 of the pullmember. Despite this, the present embodiment allows the restrainingsheath 4 to be split at the line of weakness 6 and withdrawn from beingaround the stent device 2 with a relatively low amount of pulling force,while at the same time providing a low profile region of the deliverydevice 1 where the stent device is placed, as low as 5 French (1.7 mm indiameter) with a bare stent and 6 French (2 mm in diameter) with acovered stent.

A method of releasing the stent device 2 according to the deliverydevice 1 of the present embodiment will now be described. The deliverydevice 1, with the restraining sheath 4 extending distally from theintroducer member 13, is fed to a treatment site. This is usually doneby passing the inner member 3 along a guide wire passing through acentral lumen of the inner member 3. The guide wire serves to guide thedelivery device 1 to the treatment site. Once positioned as desired,possibly with the aid of radiographic positioning, perhaps using thepush member 10 as a radiographic marker, the stent device 2 is released.

To release the stent device 2, a pull end of the pull member 5 is pulledupon at a proximal end thereof, which will be outside of the body. Ahandle of the delivery device may include a mechanism for gripping andpulling the pull end of the pull member 5. As the pull member 5 ispulled, the proximal force on the distal end of the restraining sheath 4by the wrap around portion 9 of the pull member 5 will cause therestraining sheath to split at the line of weakness 6. The wrap aroundportion 9 of the pull member 5 is able to progressively move proximallyas the restraining sheath 4 splits. The stent device 2 radially expandsto its original form, which is a deployed configuration, as therestraining sheath 4 splits and is withdrawn. Progressive splitting andwithdrawal of the restraining sheath 4 and release of the stent device 4to the deployed configuration is caused by continued pulling on thepulling member 5. Eventually, the restraining sheath 4 will be withdrawnpast a proximal end of the stent device 2 and the stent device 2 will befully deployed.

One can see with reference to FIG. 2, a half withdrawn restrainingsheath 4. The restraining sheath 4 that has been split and withdrawncollects between the outer part 8 and the inner part 7 of the pullmember 5 in a folded back and crumpled manner. The drawn material of therestraining sheath 4 is believed to aid in this desirable folding andcompaction as the restraining sheath 4 is withdrawn.

With the restraining sheath 4 withdrawn and the stent device 2 deployed,the delivery device, that is the introducer member 13 and the innermember 3, can be retracted, with the inner member 3 passing through thenow expanded stent device 2.

A possible method of putting together the stent device 2 and therestraining sheath 4 portion of the delivery device 1 will now bedescribed. The stent device 2 is crimped onto the inner member 3. Anylon thread 11 is attached to the inner member 3 proximally of thestent device 2 and fed over the stent device 2. At a diametricallyopposite location to the nylon thread 11, a protective strip ispositioned over the stent device. A PET material is cold drawn to forman elongate tube with polymer chains of the PET aligned to a largedegree. The cold drawing stretches and necks the material about thecrimped stent device 2 and with the nylon thread 11 and the protectivestrip 16 caught between the stent device 2 and the restraining sheath 4.The restraining sheath 4 is attached to the inner member 3 at a positionproximal of the attachment point of the fixed end of the nylon thread11. The nylon thread 11 is then folded back over the outside of therestraining sheath 4 and attached to the proximal stiffer portion 12 ofthe pull member 5. A laser device is used, after the restraining sheath4 is mounted coaxially over the stent device 2, to form perforations inthe restraining sheath 4 along an axially straight line over where theprotective strip 16 lies, thereby forming the line of weakness 6. Theprotective strip 16 is of such a material as to protect the stent device2 from damage by the laser.

FIGS. 3 and 4 show a second embodiment of the present invention. Thesame reference numerals are used to identify like components. The secondembodiment differs from the above described first embodiment in themechanism for releasing the stent device 2 from the restraining sheath4. It is the differences with the embodiment described above that arediscussed below.

The release mechanism includes a pull member 5 having a pull end and anopposing end that is formed or formable into a hook 18, as can be seenin FIG. 4. The pull member 5 defines an inner part 7 that extends alongan inside of the restraining sheath 4. The hook 18 at the end of thepull member 5 is configured to capture a distal end of the restrainingsheath 4. The end of the pull member 5 is folded back onto itself todefine an outer part 8 extending axially back from where the inner part7 came from with a wrap around portion 9, where the folding took place,between the inner part 7 and the outer part 8. The distal end of theinner part 7, the wrap around portion 9 and the outer part 8, which is aproximal projection of limited extent, together define the hook 18.

The distal tip member 15 of the delivery device 1 includes a storagerecess 17 for maintaining the hook 18 in a collapsed state duringdelivery of the delivery device 1. The collapsed state is preferablywith the inner part 7 and the outer part 8 thereof pressed against oneanother. The collapsed state could, however, be the hook memberstraightened out so that the outer part 8 is not wrapped back onto theinner part 7, but instead extends distally from the inner part 7. Thestorage recess 17 is configured such that the radial extent of the hook18 is reduced. The hook 18 is able to be retracted from the recess 17upon pulling and moving of the pull member 5. Once released from thestorage recess 17, the hook 18 radially expands so as to be configuredto capture the restraining sheath 4 between the inner and outer parts7,8 with the wrap around portion 19 engaging a distal end of therestraining sheath 4. The hook 18, once released, is to be moved yetfurther in the proximal direction before the distal end of therestraining sheath 4 is engaged and captured.

The pull end of the pull member 5 extends proximally beyond therestraining sheath 4 to be pulled on at the proximal end of the deliverydevice 1, perhaps at a proximal handle of the delivery device 1. Therestraining sheath 4 is attached to the inner member 3 at a positionaxially within the introducer member 13. In order that the pull member 5can extend inside of the restraining sheath 4 and also extend proximallytherefrom, the pull member passes through the restraining sheath 4. Asshown, the restraining sheath 4 is attached to the inner member 3, butwith the pull member 5 encased between the restraining sheath 4 and theinner member 3 in an axially slideable manner.

The pull member 5 is, in the preferred embodiment, made of a metalmaterial. A portion thereof at the distal end may be made of a shapememory material with an original configuration having the hook 18 formedand expanded. In this way, the hook 18 can be delivered in an opened orunfolded configuration and it will return to the hook form upon releasefrom the storage recess 17. Otherwise, in the preferred embodiment, thepull member 5 is formed of the same metal material. The metal materialensures the hook 18 has sufficient stiffness to maintain its hook formeven as the restraining sheath 4 imparts a force tending to open orunfold the hook 18 during splitting and withdrawal of the restrainingsheath 4. As can be seen in the figures, the pull member 5 has a reducedprofile portion 18 axially within the restraining sheath 4 and anincreased profile portion 12 proximally thereof. The reduced profileportion 18 is, in the preferred embodiment, provided by flattening thatportion of the pull member 5. In this way, a strong pull member 5 isprovided for the majority thereof, while the portion located between therestraining sheath 4 and the stent device 2 is thinned to ensure a lowprofile distal end region of the delivery device 1, where the stentdevice 2 and restraining sheath 4 are.

As in the first embodiment, the line of weakness 6 is locateddiametrically opposite to the pull member 5.

The introducer member 13 and the hook 18 are arranged so that as thehook 18 passes the distal end thereof, the hook 18 is unfolded or openedby the distal end wall of the introducer member 13. This ensures thatintroducer member 13 can maintain a reduced profile.

A method of releasing the stent device 2 from the restraining sheath 4will now be described. The pull end of the pull member 5 is pulledproximally in order to move the distal end of the pull member 5 out ofthe storage recess 17 of the distal tip member 15 attached to the innermember 3. The distal end is stored in the storage recess 17 in acollapsed hook form. Once the collapsed hook 18 moves past a restrainingwall of the storage recess 17, the hook 18 radially expands.

The hook 18 proper is continued to be moved proximally by pulling on thepull member 5 and the restraining sheath 4 is engaged by the wrap aroundportion 9 of the hook 18 and the inner and outer parts 7, 8 capture therestraining sheath 4 therebetween. With continued pulling on the pullmember 5, the hook 18 tugs on the distal end of the restraining sheath 4causing it to split at the line of weakness 6 and causing therestraining sheath 4 to be moved proximally out of the way of the stentdevice 2 as it radially expands into its deployed configuration.

With reference to FIG. 4, the hook 18 moves progressively proximally,causing the sheath 4 to split at the line of weakness 6. The splitsheath material is gathered by the hook 18 and the stent device 2 isreleased into its radially expanded deployed configuration. Gatheringthe split material of the restraining sheath 4 with the hook 18 ensuresthat sheath material is not caught between the expanded stent device 2and an inner wall of the bodily lumen.

A possible method of making the stent device 2 and the restrainingsheath 4 portion of the delivery device 1 will now be briefly described.A distal tip member 15 is attached to a distal end of the inner member3. A storage recess 17 is formed in the distal tip member 15 so as tohave a radial wall for holding the hook 18 in a collapsed configuration.A distal end region of the pull member 5 is flattened. A distal end ofthe flattened region of the pull member 5 is folded back upon itself toprovide the hook 18. The pull member 5 is fed over the stent device 2 tobe inserted with the hook 18 inserted in the storage recess 17 in acollapsed configuration with the distal end more tightly folded. At adiametrically opposite location to the pull member 5, the protectivestrip 16 is mounted to the stent device 2. A PET material is cold drawninto a restraining sheath 4 mounted coaxially over the stent device 2with the pull member 5 and the protective strip 16 trapped between thestent device 2 and the restraining sheath 4. The restraining sheath 4 isattached to the inner member 3 at a position proximal of the stentdevice 2 with the pull member 5 extending axially therethrough. A laseris used to form perforations over where the protective strip 16 lies,thereby forming the line of weakness 6.

In the above discussion, reference has been made to cold-drawn polymersas sheath material. The following disclosure gives one example as to howa stent may be loaded into a delivery sheath, which is subsequentlycold-drawn.

Reference numerals in the below disclosure relate to FIGS. 5, 6 and 7only.

FIG. 5 shows a crimped covered stent 10 ready for deploying from aloading sheath into a delivery sheath 12, by advancing the stent 10, ina loading tool 14 into the lumen 16 of the sheath 12, in the directionof arrow F.

The loading sheath is similar to a conventional stent deployment sheath,sized to be at least the length of the stent together with a furtherapproximate 20% in length to provide a tolerant landing zone for thestent. It is conventionally of a braided polymer catheter material, asis generally known in the art of stent delivery systems.

The stent 10 is a radially self-expanding nickel titanium alloy stentcovered in an ePTFE film. This covered stent is constrained by a loadingsheath 18 in a radially compact disposition. The stent is installed inthe loading sheath 18 by a “crimping” procedure known per se in which ajig (not shown) compresses the stent radially inwardly, down to itscompact disposition, whereupon the stent 10 and the loading sheath 18are moved relative to each other axially (usually by holding the sheath18 stationary and translating the stent 10 into the lumen of the sheath18).

In the present example, before the stent is crimped, there is insertedin its lumen a shaft 24 carrying a sequence of rings standing proud ofthe cylindrical surface of the shaft, or a spiral thread 22 runningalong the shaft. The covered stent is crimped down onto the shaft,whereupon the shaft can push the stent along its axis, supporting thestent all the way along the length of the stent, within its lumen.

The stent 10 is then “deployed” into the lumen 16 of the delivery sheath12. For that deployment, the confining sheath 18 is pulled proximally bya pulling tube 26 contiguous with the proximal end 28 of the loadingsheath 18.

During this pulling, one restrains the shaft 24 from axial movement,which prevents the stent from moving axially with the retreating loadingsheath 18, so that the sheath remains in the desired location, insidethe delivery sheath 12.

The delivery sheath 12 is of rather thin-walled PET tubular material. Itis gripped at its proximal end 30 by an annular gripper chuck 32 andgripped at its distal end 34 by a similar annular gripping chuck 36, sothat the two chucks 32 and 36 hold the opposite ends 30 and 34 of thedelivery sheath 12 at a desired distance apart, while the stent isdeployed into the sheath lumen 16.

This deployment process can be seen, partially completed, in FIG. 5 ofthe drawings, where like reference numerals identify the same componentsas are shown in FIG. 5. It will be appreciated that the loading sheath18 has moved proximally, in the direction of arrow f, relative to thestent and to the stent pusher annulus 22, thereby releasing the stent 10into the lumen 16 of the delivery sheath 12 progressively, starting atthe distal end 40 of the stent, through a radially expanding portion 42of the stent that travels the full length of the stent, from the distalend 40 to the proximal end 44 of the stent, not yet free of theconfining loading sheath 18 as shown in FIG. 6. Once the full length ofthe stent 10 is clear of the loading sheath 18, the full radiallyoutwardly directed stenting force from the stent 10 is carried by thedelivery sheath 12, and the lumen 46 of the stent is big enough forsimple proximal withdrawal from that lumen of the tubular element 24 ofthe loading machine.

The pull member and the protective strip can be incorporated into thedelivery system and placed in the correct positions within the deliverysheath prior to deployment of the stent from the loading sheath into thedelivery sheath. The stent may then be deployed against the pull memberand the protective strip, to reach the desired configuration.

As explained above, the stent 10 is now radially confined within thedelivery sheath 12 and can be regarded as a precursor for a “capsule”for placement at the distal end of a catheter delivery system for thestent. If desired, the loading sheath can be reused a number of times,for example ten times, before it is replaced.

The process is presented in a block diagram, in drawing FIG. 7. However,FIG. 7 identifies further steps of the manufacturing process. Thesequence of steps in FIG. 7 is identified by references A to I and wehave the following comments on these process steps.

Step A is the step of providing the stent or stent graft of choice. Abare stent is one without any covering. A stent graft is a covered barestent and the covering is typically of expanded polytetrafluoroethylene(ePTFE) but other covering materials are known to those skilled in theart.

Step B is the step of installing in the lumen of the chosen stent aninner catheter tool and the one preferred by the present Applicant isthat described in its earlier publication WO 2004/096091 which goes bythe acronym “ALFER”.

Step C is the step of crimping the stent to bring the outside diameterof the chosen stent down to one that is small enough for loading thecrimped stent into the chosen loading sheath 18. Next, step D, thecrimped stent is translated axially into the lumen of the loading sheath18. Then, the loading sheath carrying the stent is translated (asexplained in FIGS. 5 and 6) into the lumen 16 of the delivery sheath 12and the loading sheath 18 is withdrawn in order to deploy the stent intothe delivery sheath. As noted on FIG. 7, the delivery sheath 12 isconveniently a PET tube having a length about three times that of thestent, with a pre-thinned zone in the PET tube located midway along thelength of the stent in the lumen of the PET tube.

Once the stent is deployed, the inner catheter loading tool can beremoved, step F, from the lumen of the deployed stent. At this point,step G, any desired component of the catheter delivery system which isto be located in the lumen of the stent can now be introduced into thatlumen.

Of course, other methods of deploying stents into the lumens of e.g.body passages are known by those skilled in the art, and may withappropriate modification be employed to deploy the stent from theloading sheath to the delivery sheath in an equivalent manner.

Having prepared the stent lumen, the delivery sheath can now becold-drawn, lengthwise, to impose substantial strain on the material ofthe delivery sheath. This strain will have the effect of reducing thewall thickness of the delivery sheath, and generating hoop stresseswithin the delivery sheath being cold-drawn, which hoop stresses willtend to compress the stent inside the lumen of the delivery sheath, andtherefore marginally reduce its diameter. The FIG. 7 block diagramcarries notes in relation to this step H of the process. These notesteach to use a soft sticky material to grip the delivery sheath forachieving the cold-drawing strain. Such soft, sticky materials could besilicone rubber or an adhesive composition, for example. That strain isconveniently imposed on the sheath stepwise, commencing at the midpointof the length of the sheath and repeating the cold-drawing process,stepwise, until a final desired outside diameter profile is achieved forthe sheathed stent. For example, using two gripping chucks 32 and 36,the sheath is firstly gripped at each end by the two chucks. The chucksare drawn apart to create a weak zone at the middle of the sheath. Then,the sheath is simultaneously gripped in the middle by the first grippingchuck and at one end by the second gripping chuck, then the grippingchucks are slowly drawn apart. The second gripping chuck is now moved tothe new middle of the drawn sheath, and the first gripping chuck to theother end. The gripping chucks are again drawn apart. This process isrepeated until a desired delivery sheath diameter is reached.

Thus, in the final step I of the process, the stent-bearing capsule isready for combining with other components of the catheter system that isto deliver the stent to the site of stenting in the body of a patient.This is done in an entirely conventional manner, for exampleheat-melting the inner catheter 24 with a member of the same diameter inthe proximally proximate component of the delivery system.

The above has described two preferred embodiments of the invention.Modifications to these preferred embodiments are possible and would berealised by the skilled person.

For example, one can imagine the hook 18 of the second embodiment wouldnot necessarily need to be upwardly facing. The distal end of the pullmember 5 forming the short part of the hook 18 could face inwardlytowards the stent device 2. One can also envisage this inwardly facinghook 18 being positioned between the stent device 2 and the restrainingsheath 4 and the remainder of the pull member 5 being outside of therestraining sheath 4. The hook 18 would thus be tucked into therestraining sheath 4 at the distal end in the delivery configuration,thereby offering a protective mechanism against the projection of thehook 18 damaging tissue. The storage recess 17 could thus be done awaywith.

One can also envisage a modification whereby the restraining sheath 4 iswithdrawn distally rather than proximally as in the preferredembodiments. This modification has the pull member 5 extending throughthe lumen of the inner member 3 and out of the distal end of thedelivery device 1. The pull member 5 could then be wrapped back aroundthe distal end of the delivery device 1. The pull member 5 is then fedproximally between the stent device 2 and the restraining sheath 4 andwrapped around the proximal end of the restraining sheath 4 using a wraparound form as in the first embodiment or a hook wrap form as in thesecond embodiment. In this way, pulling on the pull member 5 will causethe sheath 4 to be retracted progressively from the proximal end to thedistal end.

Another modification to the first embodiment that can be imagined is toattach the fixed end of the pull member 5 to the inner wall of theintroducer member 13. The restraining sheath 4 could also be attached tothe inner wall of the introducer member 13 at a location proximal of theattachment of the pull member 5. The pull member 5 will thus extendoutside of the restraining sheath 4, wrap around the distal end of therestraining sheath and return inside of the restraining sheath 4proximally to provide the pull end.

It can thus be seen that modifications to the presently preferredembodiments would be contemplated by the skilled person, while using thegeneral concepts of the present invention set out in the claims andelsewhere herein.

What is claimed is:
 1. A delivery device, comprising: a stent device,which is radially expandable from a radially reduced, deliveryconfiguration to a radially expanded, deployment configuration; arestraining sheath mounted coaxially over the stent device formaintaining the stent device in the delivery configuration, therestraining sheath having a line of weakness extending axially; a pullmember to be pulled so as to split the restraining sheath at the line ofweakness and withdraw the restraining sheath from over the stent device,wherein: the pull member and the line of weakness are located onopposing sides of the restraining sheath; and the pull member has aninner part extending inside of the restraining sheath, an outer partextending outside of the restraining sheath, and a wrap around portiontherebetween for wrapping around an axial end of the restraining sheathto radially capture the restraining sheath between the inner and outerparts.
 2. The delivery device of claim 1, wherein the line of weaknessand the pull member are located substantially diametrically opposite oneanother.
 3. The delivery device of claim 1 wherein the line of weaknessis a line of perforations.
 4. The delivery device of claim 1, whereinthe pull member is attached to the delivery device and fixed relative tothe restraining sheath at one end and an opposing end provides a pullend to be pulled in order to affect splitting and withdrawing of therestraining sheath and wherein between the opposing ends, the pullmember wraps around the axial end of the restraining sheath.
 5. Thedelivery device of claim 4, wherein the stent device is supported on aninner member.
 6. The delivery device of claim 5, wherein the innermember extends proximally from the stent device and the fixed end of thepull member is attached to the inner member so that the pull memberextends therefrom inside of the restraining sheath, wraps around adistal end of the restraining sheath and returns proximally on theoutside of the restraining sheath to provide the pull end.
 7. Thedelivery device of claim 6, wherein the restraining sheath is attachedto the inner member at a position proximal of where the fixed end of thepull member is attached.
 8. The delivery device of claim 4, wherein atleast a portion of the pull member is a polymer thread.
 9. The deliverydevice of claim 8, wherein the polymer thread is a nylon thread.
 10. Thedelivery device of claim 8, wherein the pull member comprises a stiffermetal portion attached to the polymer thread portion at a positionproximal of the stent device.
 11. The delivery device of claim 1,wherein at least a portion of the pull member extending axially, andradially between the restraining sheath and the introducer sheath, isflattened.
 12. The delivery device of claim 1, wherein the restrainingsheath is formed of an axially cold drawn polymer material.
 13. Thedelivery device of claim 12, wherein the material of the restrainingsheath is poly(ethylene terephthalate) (PET).
 14. The delivery device ofclaim 1, further comprising a strip of protective material locatedradially between the line of weakness of the restraining sheath and thestent device.
 15. The delivery device of claim 1, wherein the pullmember forms a hook at one end and an opposing end provides a pull endto be pulled in order to affect splitting and withdrawing of therestraining sheath, wherein the hook is for radially capturing an insideand an outside of the restraining sheath between the inner and outerparts thereof.
 16. A method of medical treatment, comprising: providinga stent delivery device comprising: a radially expandable stent devicedisposed at a distal portion of the stent delivery device; a restrainingsheath mounted coaxially over the stent device for maintaining the stentdevice in a reduced diameter delivery configuration, wherein therestraining sheath includes a line of weakness extending axially; a pullmember disposed along a different region of the restraining sheath fromthe line of weakness, wherein the pull member has an inner partextending inside of the restraining sheath, an outer part extendingoutside of the restraining sheath, and a wrap around portiontherebetween for wrapping around an axial end of the restraining sheath;advancing the distal portion of the stent delivery device to a desiredlocation; pulling on the pull member so as to split the restrainingsheath at the line of weakness and withdraw the restraining sheath fromover the stent device while radially capturing the restraining sheathbetween the inner and outer parts, such that the stent is allowed toexpand.
 17. The method of claim 16, wherein the pull member is attachedto the delivery device and fixed relative to the restraining sheath at afixed end and an opposing end provides a pull end to be pulled in orderto affect splitting and withdrawing of the restraining sheath andwherein between the opposing ends, the pull member wraps around theaxial end of the restraining sheath, and wherein the step of pulling onthe pull member includes pulling on the pull end.
 18. The method ofclaim 17, wherein the stent device is supported on an inner memberextending proximally from the stent device and the fixed end of the pullmember is attached to the inner member so that the pull member extendstherefrom inside of the restraining sheath, wraps around a distal end ofthe restraining sheath and returns proximally on the outside of therestraining sheath to provide the pull end, and wherein the step ofpulling on the pull member includes pulling on the pull end.